Air bag gas generator and air bag device

ABSTRACT

The present invention provides a gas generator in which the entire size of a container is small, the generator can be produced easily with a simple structure, the output of a gas generator is equalized so that an occupant can be safely restrained, and the combustion performance can be stably adjusted.  
     A gas generator for an air bag comprises a housing forming an outer shell container and accommodating two or more ignition means to ignite on an impact and two or more gas generating means which are to be independently ignited and burnt by the ignition means so as to generate a combustion gas for inflating an air bag, and a plurality of gas discharge ports which are formed in the housing, wherein the gas discharge ports are closed by sealing means for maintaining an internal pressure of the housing to the given pressure, a breaking pressure for breaking the sealing means is adjusted at multiple stages by controlling gas discharge ports and/or sealing means, and a difference of the maximum internal pressures in the housing at activation of the respective igniters is suppressed.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a gas generator for an air bagand an air bag apparatus including two or more ignition means and two ormore gas generating means for controlling discharge of gas or behaviorof flow of the gas.

PRIOR ART

[0002] An air bag system which is mounted on various kinds of vehiclesand the like including automobiles, aims to hold an occupant by means ofan air bag (a bag body) rapidly inflated by a gas when the vehiclecollides at a high speed so as to prevent the occupant from crashinginto a hard portion inside the vehicle such as a steering wheel, awindscreen due to an inertia and being injured. This kind of air bagsystem generally comprises a gas generator to be actuated according to acollision of the vehicle and discharge a gas, and an air bag tointroduce the gas to inflate.

[0003] It is desired that the air bag system of this type can safelyrestrain the occupant even when frame of the occupant (for example,whether a sitting height is long or short, whether an adult or a child,and the like), a sitting attitude (for example, an attitude of holdingon the steering wheel) and the like are different. Then, there has beenconventionally suggested an air bag system which actuates, applying animpact to the occupant as small as possible at the initial stage of theactuation. Gas generators in such a system are disclosed inJP-A8-207696, U.S. Pat. Nos. 4,998,751 and 4,950,458. JP-A 8-207696suggests a gas generator in which one igniter ignites two kinds of gasgenerating agent capsules so as to generate the gas at two stages. U.S.Pat. Nos. 4,998,751 and 4,950,458 suggest a gas generator in which twocombustion chambers are provided for controlling actuation of the gasgenerator so as to generate the gas at two stages due to a expandedflame of the gas generating agent.

[0004] However, these gas generators have drawbacks such that aninternal structure thereof is complicated, a size of a container becomesgreat, and a cost therefor becomes expensive.

[0005] Further, since the ratio between a surface area of gas generatingagent which burns at each of stages and an area of a nozzle forcontrolling the combustion is not preferable over the entire stages, theinternal pressure in the housing may be excessively low in thecombustion of the first stage and excessively high in the combustion ofthe second stage, and therefore, it is not possible to controlappropriately.

[0006] Further, in JP-A 9-183359, and DE-B 19620758, there is discloseda gas generator in which two combustion chambers storing a gasgenerating agent are provided in a housing and an igniter is arranged ineach combustion chamber, so as to adjust an activation timing of each ofthe igniters, thereby adjusting an output of the gas generator. However,in any of the gas generators, since the igniters arranged in therespective combustion chambers are independently arranged, it becomeshard to assemble (manufacture), the structure itself of the gasgenerator becomes complicated and a volume thereof becomes large.

DISCLOSURE OF THE INVENTION

[0007] Accordingly, the present invention provides a gas generator whichactuates, applying as small an impact as possible to an occupant at theinitial stage of an actuation and can widely and optionally adjust anoutput and timing of an output increase of the gas generator so as tosafely restrain the occupant even when frame of the occupant (forexample, whether a sitting height is long or short, whether an adult ora child, and the like), a sitting attitude (for example, an attitude ofholding on the steering wheel) and the like are different, and also canstabilize a combustion performance as well as restricting the total sizeof a container, having a simple structure, and being easily manufacturedand lightweight.

[0008] A gas generator for an air bag of the present invention includestwo or more ignition means in a housing, and is characterized in acombination of a gas discharge port or gas discharge ports which areformed in the housing and sealing means such as a seal tape for closingthe gas discharge port. When a plurality of combustion chambers areprovided in the housing, respective gas generating means accommodated ineach combustion chamber are independently ignited and burntsimultaneously or at intervals by different ignition means. And bycontrolling a diameter of the opening (opening area) of the gasdischarge port and/or a thickness of the seal tape which closes the gasdischarge port, it is possible to equalize the pressure (hereinafterreferred as “combustion internal pressure”) in the housing when the gasgenerating means burns and also to stabilize the combustion performance.

[0009] Namely, the present invention provides the gas generator for anair bag which comprises a housing forming an outer shell container andaccommodating two or more ignition means to ignite on an impact and twoor more gas generating means which are to be respectively ignited andburnt by the ignition means so as to generate a combustion gas forinflating an air bag, and a plurality of gas discharge ports which areformed in the housing and closed by sealing means for maintaining aninternal pressure of the housing to the given pressure, wherein abreaking pressure for breaking the sealing means is adjusted at multiplestages by two or more gas discharge ports and/or two or more sealingmeans.

[0010] Preferably, a difference in the maximum internal pressures in thehousing at the time of activation of the respective ignition means issuppressed.

[0011] The breaking pressure can be adjusted by either one of an openingdiameter, an opening area of the gas discharge port and the sealingmeans, or by a combination thereof. That is, the opening diameter can bechanged between 1 and 8 mm, or 1.2 and 4 mm. With respect to the gasdischarge ports being next to each other in breaking pressure forbreaking the sealing means, a ratio of different breaking pressuresthereof is 1.1/1 or greater, and more preferably, 4/1 to 1.1/1.

[0012] The opening area and the ratio of the opening area are changed inaccordance with the amount of the gas generating agent or a surface areaof the agent. The thickness of the sealing means is changed inaccordance with the ratio of the opening area or the amount of the gasgenerating agent or the surface area of the agent.

[0013] The amount and shape of the gas generating agent can beindividually and optionally set for each of the plurality of combustionchambers. The amount of generated gas is largely varied by the number ofignitions and igniting timing. Therefore, in comparison with thegenerator having a single ignition means, there exist a plurality of gasgenerating behavior, i.e., output characteristics, and any one of themcan be selected. The combustion internal pressure depends on the ratiobetween the surface area and the opening area of the gas generatingagent. When there are a plurality kinds of gas generating agents, thesurface area of the gas generating agent, i.e., the combustion surfacearea is changed by the number of the ignitions and the igniting timing.

[0014] The breaking pressure is adjusted by arranging two or more kindsof opening diameters and/or opening areas of the gas discharge port. Itis preferable that among two kinds or more of the gas discharge portsformed in the housing, with respect to two kinds of openings being nextto each other in size of the opening diameter thereof, a ratio betweenthe larger diameter-having gas discharge port and the smallerdiameter-having gas discharge port is 4/1 to 1.1/1 and/or a ratio inopening area is 97/3 to 3/97.

[0015] Further, the breaking pressure is adjusted by arranging two ormore kinds of thicknesses of the sealing means. It is preferable thatamong sealing means having two kinds or more of thicknesses, withrespect to the sealing means being next to each other in thickness, athickness ratio between them is 1.1/1 to 12/1. The breaking pressure isadjusted by setting an area ratio of the two kinds or more of dischargeports having different areas that are sealed by the sealing means havingtwo or more different thicknesses is 97/3 to 3/97.

[0016] Further, in the present invention, the breaking pressure can beadjusted by arranging two or more kinds of opening diameters and/oropening areas of the gas discharge ports, and by arranging two or morekinds of thicknesses of the sealing means. Also in this case, a ratio ofarea of the two kinds or more of discharge ports sealed by the sealingmeans having two or more different thicknesses can be in a range of 97/3to 3/97.

[0017] Further, it is preferable that the sealing means is a seal tapecomprising a seal layer having a thickness of 20 to 200 μm and a bondinglayer or an adhesive layer having a thickness of 5 to 100 μm. In thepresent invention, the thickness of the seal tape means a thicknesscomprising the seal layer and the bonding layer or the adhesive layer.In the sealing means such as the seal tape, the breaking pressure isadjusted by a size of the gas discharge port and/or a thickness thereof,but the maximum internal pressure in the housing at the time ofcombustion of the gas generating means (hereinafter, refer to as “acombustion maximum internal pressure”) and the combustion performance ofthe gas generating means are not adjusted.

[0018] That is, in the gas generator of the present invention, a maximumcombustion internal pressure at the time of combustion of the gasgenerating means is adjusted by the opening area of the gas dischargeport. As a result, even after the seal tape is broken, the internalpressure in the housing can be adjusted by the relation between theopening area and the combustion performance of the gas generating means.It is preferable that the sealing means (especially when the sealingmeans is a seal tape) includes a moisture-proof function for preventingmoisture from entering the housing. In the present invention, when aconstituent element which requires the moisture-proof function such asthe gas generating means is additionally provided with themoisture-proof means, the sealing means can be satisfactory only if thebreaking pressure thereof is adjusted at multiple stages. As such aadditional moisture-proof means, in the case of the gas generating meansfor example, a means such as one enveloping with a moisture-proof sheetcan be mentioned.

[0019] In the gas generator of the present invention, a plurality ofcombustion chambers are provided in the housing, each of the gasgenerating means for generating the combustion gas is accommodated inindividual combustion chamber and independently ignited by therespective ignition means. With this structure, a flame generated bycombustion of a gas generating means cannot be transferred to the othergas generating means. It is preferable that the gas generating meansaccommodated in the respective combustion chambers are the solid gasgenerating agents having a different surface area per unit weight fromeach other. For example, when two combustion chambers accommodating thegas generating means are provided in the housing, the combustionchambers can be concentrically provided so as to be adjacent in theradial direction of the housing, or the housing can be formed into acylindrical shape having an axial core length longer than an outermostdiameter, and the combustion chambers can be concentrically provided soas to be adjacent in the axial direction and/or a radial direction ofthe housing. In this case, a communication hole which allowscommunication between the combustion chambers can be provided. In therespective combustion chambers provided in the above way, the gasgenerating means are accommodated and burnt independently. Thesecombustion chambers is a chamber exclusively used for accommodating thegas generating means, and even if the ignition means includes thetransfer charge, the chambers can be distinguished from the space inwhich the transfer charge is accommodated.

[0020] The structural requirements of a dual pyrotechnic inflatoraccording to the present invention having a plurality of openings andthe equalized combustion internal pressure (the stabilized combustionperformance) are that two or more ignition means and a housing foraccommodating the gas generating agent are provided, the housing isprovided with two kinds or more of nozzles having different openingdiameter/opening area, and/or the thickness of the sealing means whichcloses the gas discharge port is controlled in two kinds or more. Forexample, the present invention is characterized in that a large nozzleand a small nozzle are formed, the large nozzle is broken at the initialstage of activation of the dual pyrotechnic inflator, i.e., by theignition of the gas generating agent in the first chamber, and the smallnozzle is opened later than, or simultaneously with the large nozzle atthe later stage, i.e., when the gas generating agent in the secondchamber is ignited or the two igniters simultaneously ignite and the gasgenerating agents in both the chambers are burnt. It is another objectof the present invention to have a different charged amount ofpropellant (between the first chamber and the second chamber). Forexample, the large nozzle is opened at the internal pressure of 100kg/cm², and when the internal pressure reaches 150 kg/cm² or greater,the small nozzle is also opened. In order to achieve this, it ispossible to change the diameter of the nozzle of the gas discharge portwhile keeping the thickness of the seal tape constant, or to change thethickness of the seal tape while keeping the diameter of the nozzleconstant. By controlling the diameter of the gas discharge port and/orthe breaking pressure of the sealing means in the above way, forexample, in a case that the two combustion chambers are provided in thehousing and that the first gas generating means and the second gasgenerating means are separated and accommodated in the respectivecombustion chambers, combustion of any gas generating means can beperformed constantly under the ideal combustion conditions (e.g.,combustion internal pressure and the like). In other words, if all ofthe gas discharge ports are opened at the initial stage, appropriatecombustion environment can be obtained in the case of burningsimultaneously the first and second gas generating means. However, inthe case of burning the second gas generating means after about 30milliseconds, the combustion gas of the first gas generating means hasbeen discharged during that period, by whereby the combustion internalpressure at the time of burning the second gas generating means becomesslitly lower as compared with the case when the two gas generating meansare burnt simultaneously, and it is not optimal combustion environmentfor burning the second gas generating means. If the opening area of thegas discharge port is adjusted to be small to compensate this defect, inthe case that the second gas generating means is burnt after 10milliseconds or 20 milliseconds, or in the case that the gas generatingmeans are burnt simultaneously, the pressure at combustion becomeshigher. Accordingly, if one kind of gas discharge ports are opened atone time from the initial stage, it is difficult to meet all of thecombustion modes. And as a result, the combustion internal pressure whenthe first gas generating agent is burnt is low, which brings a greatdifference with the internal pressure when the second gas generatingagent is burnt. Thereupon, in such a gas generator, if a plurality ofgas discharge ports, for example, comprising a gas discharge port to beopened when the first gas generating means is burnt and a gas dischargeport to be opened when the second gas generating means is burnt areadjusted to be opened at different timings in accordance with thecombustion of each of the gas generating means, the gas generating meanscan be burnt constantly under the ideal combustion condition (thecombustion internal pressure).

[0021] Further, in the case of characteristically adjusting theactuation performance of the gas generator, particularly a change withthe passage of time in the gas discharge amount, two combustion chambersare charged with the gas generating means which are different in atleast one of a burning rate, a composition, a composition ratio and anamount from each other, respectively, and the respective gas generatingmeans can be independently ignited and burnt at an optional timing.Further, at each combustion chamber, the gas generating means having adifferent gas amount generated at a unit time may be stored.

[0022] As the gas generating means, in addition to an azide gasgenerating agent based on an inorganic azide which has been widely used,for example, a sodium azide, a non-azide gas generating agent not basedon an inorganic azide may be used. However, from the view of safety, thenon-azide gas generating agent is preferable, and as the non-azide gasgenerating composition, for example, a composition containing a nitrogencontaining organic compound such as a tetrazole, a triazole or ametallic salt thereof and an oxygen containing oxidant such as an alkalimetal nitrate, a composition using a triaminoguanidine nitrate, acarbohydroazide, a nitroguanidine and the like as a fuel and nitrogensource and using a nitrate, chlorate, a perchlorate or the like of analkali metal or an alkaline earth metal as an oxidant, and the like maybe employed. In addition, the gas generating means can be suitablyselected according to requirements such as a burning rate, anon-toxicity, a combustion temperature, a decomposition startingtemperature. In the case of using the gas generating means havingdifferent burning rates in the respective combustion chambers, may beused the gas generating means having the different composition orcomposition ratio itself, such that, for example, the inorganic azidesuch as the sodium azide or the non-azide such as the nitroguanidine isused as the fuel and the nitrogen source. Alternatively, the gasgenerating means obtained by changing a shape of the composition to apellet shape, a wafer shape, a hollow cylindrical shape, a disc shape, asingle hole body shape or a porous body shape, or the gas generatingmeans obtained by changing a surface area according to a size of aformed body may be used. In particular, when the gas generating means isformed into the porous body with a plurality of through holes, anarrangement of the holes is not particularly limited, however, in orderto stabilize a performance of the gas generator, an arrangementstructure such that a distance between an outer end portion of theformed body and a center of the hole and a distance between each centerof the holes are substantially equal to each other is preferable.Concretely, in the cylindrical body having a circular cross section, forexample, a preferred structure is such that one hole is arranged at thecenter and six holes are formed around the hole so that the center ofeach hole is the apex of regular triangles of the equal distancesbetween the holes. Further, in the same manner, an arrangement such thateighteen holes are formed around one hole at the center may be alsosuggested. However, the number of the holes and the arrangementstructure are determined in connection with an easiness formanufacturing the gas generating agent, a manufacture cost and aperformance, and are not particularly limited.

[0023] Additionally, the housing may contain a coolant means for coolingthe combustion gas generated due to combustion of the gas generatingmeans on the side of a peripheral wall of the housing thereof. Thecoolant means is provided in the housing for the purpose of coolingand/or purifying the combustion gas generated due to the combustion ofthe gas generating means. For example, in addition to a filter forpurifying the combustion gas and/or a coolant for cooling the generatedcombustion gas which have been conventionally used, a layered wire meshfilter obtained by forming a wire mesh made of a suitable material intoan annular layered body and compress-molding, and the like can be used.The layered wire mesh coolant can be preferably obtained by forming aplain stitch stainless steel wire mesh in a cylindrical body, foldingone end portion of the cylindrical body repeatedly and outwardly so asto form an annular layered body and then compress-molding the layeredbody in a die, or by forming a plain stitch stainless steel wire mesh ina cylindrical body, pressing the cylindrical body in the radialdirection so as to form a plate body, rolling the plate body in acylindrical shape at many times so as to form the layered body and thencompress-molding it in the die. Further, the coolant with a doublestructure with different layered wire mesh bodies at an inner side andan outer side thereof, which has a function for protecting the coolantmeans in the inner side and a function for suppressing expansion of thecoolant means in the outer side, may be used. In this case, it ispossible to restrict the expansion by supporting an outer periphery ofthe coolant means with an outer layer such as the layered wire meshbody, the porous cylindrical body, the annular belt body.

[0024] And in the case of the gas generator in which the combustion gasgenerated due to the combustion of the gas generating means stored intwo combustion chamber reaches the gas discharge port via a differentflow paths in each combustion chamber so that the gas generating meansstored in one combustion chamber is not directly ignited due to thecombustion gas generated in the other combustion chambers, the gasgenerating means in the combustion chambers burns in each chamber in acompletely independent manner, and therefore, the gas generating meansin each combustion chamber is ignited and burnt in more secure manner.As a result, even when activation timings of two igniters are staggeredsignificantly, the flame of the gas generating means in the firstcombustion chamber ignited by the firstly actuated igniter does not burnthe gas generating means in the other combustion chambers, so that astable output can be obtained. This kind of gas generator can beachieved, for example, by arranging a flow passage forming member in thehousing so as to form the flow passage and introducing the combustiongas generated in the first combustion chamber to the coolant meansdirectly.

[0025] The housing mentioned above can be obtained by forming a diffusershell having a gas discharge port or gas discharge ports and a closureshell, which forms a storing space together with the diffuser shell,with a casting, a forging, a press-molding or the like, and joining bothshells. The joining of both shells can be performed by various kinds ofwelding methods, for example, an electronic beam welding, a laserwelding, a TIG arc welding, a projection welding, or the like. Formingthe diffuser shell and the closure shell by press-molding various kindsof steel plates such as the stainless steel plate makes manufacture easyand reduces a manufacturing cost. Further, forming both shells into asimple shape as cylindrical shape makes the press-molding of the shellseasy. With respect to the material of the diffuser shell and the closureshell, the stainless steel is preferable, and the material obtained byapplying a nickel plating to the steel plate may be also acceptable.

[0026] In the housing mentioned above, the ignition means to be actuatedby detecting the impact and ignite and burn the gas generating means isfurther installed. In the gas generator according to present invention,as the ignition means, an electric ignition type ignition means to beactivated by an electric signal (or an activating signal) transmittedfrom an impact sensor or the like which detects the impact is used. Theelectric ignition type ignition means comprises an igniter to beactivated by the electric signal transmitted from the electric sensorwhich exclusively detects the impact by means of an electric mechanismsuch as a semiconductor type acceleration sensor or the like, and atransfer charge to be ignited and burnt by the activation of the igniteras required.

[0027] This transfer charge should be distinguished from the gasgenerating means in that the transfer charge is for burning the gasgenerating means by the combustion gas thereof and not for directlyinflating the air bag. When each of the two or more ignition meansincludes an igniter, in order to facilitate the mounting operation ofthe igniters, it is preferable that the respective igniters constitutingthe ignition means are provided in one initiator collar so as to bealigned to each other in the axial direction. When the ignition meansalso comprises a transfer charge to be ignited and burnt on activationof the igniter, it is preferable that the transfer charge is partitionedfor each igniter and independently ignited and burnt at each igniter sothat flame caused by combustion of the transfer charge corresponding toany one of the igniters does not directly ignite the transfer chargecorresponding to another igniter. As such a structure, for example, itis possible that each igniter is disposed in an independent igniteraccommodating chamber, and the transfer charge is disposed in theigniter accommodating chamber, or the transfer charge is disposed in aposition inside the independent combustion chamber where the transfercharge can be ignited and burnt. When the transfer charge is partitionedfor each igniter, the respective gas generating means accommodated inthe two or more combustion chambers can be ignited and burnt by flamecaused by combustion of the transfer charge in different section. And inaccordance with combustion of the gas generating means accommodated ineach of the combustion chambers, any one of the plurality of gasdischarge ports is opened, and thereby the gas generating means in eachof the combustion chambers can be burnt under the ideal combustioninternal pressure.

[0028] The two or more ignition means disposed in the housingrespectively includes the igniter to be activated by an electric signal,the igniters are provided in one initiator collar so as to be aligned toeach other in the axial direction, and each igniter can be arrangedeccentrically with respect to the center axis of the housing. It ispreferable that lead wires for transmitting the electric signals arerespectively connected to the igniters, and the lead wires are taken outin the same direction on the same plane. Further, the lead wires arepreferably connected via connectors, and the connectors are preferablyarranged in the same direction on the same plane. It is preferable thatthe lead wires are taken out by the connector in the same direction aswell as the direction perpendicular to the axial direction of thehousing, and that the connector includes positioning means with adifferent chape for each igniter to be connected or with projection andrecess so as to be capable of connecting only one igniter.

[0029] The present invention provides a gas generator for an air bag,comprising a housing forming an outer shell container and accommodatingtwo or more ignition means to ignite on an impact and two or more gasgenerating means which are to be independently ignited and burnt by theignition means to generate a combustion gas for inflating an air bag,and a plurality of gas discharge ports which are formed in the housingand closed by sealing means for maintaining an internal pressure of thehousing to the given pressure, wherein a first combustion chamber whichstarts burning first and a second combustion chamber which startsburning later are partitioned with a wall having a communication hole,the communication hole is provided with flame-transfer-preventing meansso that the combustion should not be caused in the second combustionchamber by the combustion in the first combustion chamber.

[0030] The flame-transfer-preventing means may be a sealing member suchas a seal tape or a sealing plate. The sealing member may also seal thecommunication hole on the side of the first combustion chamber.

[0031] Further, the present invention provides a gas generator for anair bag, comprising a housing forming an outer shell container andaccommodating two or more ignition means to ignite on an impact and twoor more gas generating means which are to be independently ignited andburnt by the ignition means to generate a combustion gas for inflatingan air bag, and a plurality of gas discharge ports which are formed inthe housing and closed by sealing means for maintaining an internalpressure of the housing to the given pressure, wherein a firstcombustion chamber which starts burning first is partitioned with a wallfrom a second combustion chamber which starts burning later, and thegases generated in the respective combustion chambers pass through thedifferent passages and reach the gas discharge ports.

[0032] The different passages may be formed by passage-forming members.

[0033] The gas generator for the air bag mentioned above is accommodatedin a module case together with the air bag (the bag body) to introducethe gas generated in the gas generator and inflate, so as to form theair bag apparatus. In this air bag apparatus, the gas generator isactuated when reacting on the impact detected by the impact sensor, andthe combustion gas is discharged from the gas discharge port in thehousing. The combustion gas is flowed into the air bag, by whereby theair bag breaks the module cover to inflate, and forms a cushion forabsorbing the impact between the hard member in the vehicle and theoccupant.

[0034] The present invention can be realized by combining two or morestructural requirements and functions described above.

[0035] The present invention provides a gas generator which has astabilized actuation performance at the all stages of actuation thereof,and actuates, applying as small an impact as possible to an occupant atthe initial stage of an actuation and can widely and optionally adjustan output and timing of an output increase of the gas generator so as tosafely restrain the occupant even when frame of the occupant (forexample, whether a sitting height is long or short, whether an adult ora child, and the like), a sitting attitude (for example, an attitude ofholding on the steering wheel) and the like are different.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a vertical cross sectional view showing one embodimentof a gas generator of the present invention;

[0037]FIG. 2 is a vertical cross sectional view showing anotherembodiment of a gas generator of the invention;

[0038]FIG. 3 is a vertical cross sectional view showing anotherembodiment of a gas generator for an air bag of the invention;

[0039]FIG. 4 is a vertical cross sectional view showing still anotherembodiment of a gas generator for an air bag of the invention;

[0040]FIG. 5 is a vertical cross sectional view showing anotherembodiment of a gas generator for of the invention;

[0041]FIG. 6 is an exploded perspective view showing a partition wall;

[0042]FIG. 7 is a vertical cross sectional view showing still anotherembodiment of a gas generator for an air bag of the invention;

[0043]FIG. 8 is a perspective plan view of the gas generator shown inFIG. 7;

[0044]FIG. 9 is a sectional view of an essential portion showing anopening;

[0045]FIG. 10 is a perspective view of an essential portion showing apositioning structure of an igniter and a cable;

[0046]FIG. 11 is a sectional view of an essential portion showinganother mode of a coolant/filter;

[0047]FIG. 12 is a vertical cross sectional view showing a mode in whichan automatic ignition material is disposed;

[0048]FIG. 13 is a view showing a structure of an air bag apparatus ofthe invention; and

[0049]FIG. 14 is a view showing a structure of an air bag apparatus ofthe invention and showing two passages.

[0050] Reference of numerals

[0051]3 Housing

[0052]5 a First combustion chamber

[0053]5 b Second combustion chamber

[0054]7 Partition wall

[0055]9 a First gas generating agent

[0056]9 b Second gas generating agent

[0057]12 a First igniter

[0058]12 b Second igniter

[0059]13 Initiator collar

[0060]22 Coolant/filter

[0061]26 a First gas discharge port

[0062]26 b Second gas discharge port

[0063]27 Seal tape

[0064]27 a First seal tape

[0065]27 b Second seal tape

PREFERRED EMBODIMENTS OF The INVENTION

[0066] A gas generator for an air bag according to the present inventionwill be described below on the basis of embodiments illustrated in theaccompanying drawings.

[0067] Embodiment 1

[0068]FIG. 1 is a vertical cross sectional view of a first embodiment ofa gas generator for an air bag according to the present invention, whichshows a structure particularly suitable for being arranged in a driverside.

[0069] The gas generator comprises a housing 3 which is formed byjoining a diffuser shell 1 with gas discharge ports and a closure shell2 forming a inner accommodating space with the diffuser shell, and aninner cylindrical member 4 formed in a substantially cylindrical shapearranged in the housing 3, thereby forming a first combustion chamber byan outer side of the inner cylindrical member 4. Further, a steppednotch portion 6 is provided inside the inner cylindrical member, apartition wall 7 formed in a substantially flat circular shape isarranged in the stepped notch portion, the partition wall furtherpartitions an inner portion of the inner cylinder into two chambers soas to form a second combustion chamber 5 b in the diffuser shell side(in the upper space side) and an ignition means accommodating chamber 8in the closure shell side (in the lower space side), respectively. As aresult, in this gas generator, the first combustion chamber 5 a and thesecond combustion chamber 5 b are concentrically provided in the housing3 and arranged in adjacent to each other in the radial direction of thehousing. Gas generating agents (9 a, 9 b) which is to be burnt byignition means activated on an impact so as to generate combustion gasare stored in the first and second combustion chambers, and the ignitionmeans to be actuated on an impact is stored in the ignition meansaccommodating chamber 8. A through hole 10 is provided in the innercylindrical member 4 which defines the first combustion chamber 5 a andthe second combustion chamber 5 b, and the through hole is closed by aseal tape 11. And, the seal tape 11 is ruptured when the gas generatingagent is burnt, both combustion chambers can be communicated with eachother by the through hole 10. This seal tape 11 needs to be adjusted onits material and a thickness so that the seal tape is broken exclusivelywhen the gas generating agent 9 b in the second combustion chamber 5 bis burnt. In the present embodiment, a stainless seal tape having athickness of 40 μm is used. Further, the through hole 10 does notfunction to control an internal pressure in the combustion chamber 5 bsince an opening area thereof is formed larger than a gas discharge port26 b.

[0070] The ignition means comprises two electric ignition type igniters(12 a, 12 b) to be activated by an activating signal outputted on abasis of detection by the sensor, and the igniters are provided inparallel to each other in one initiator collar 13 so as to exposing headportions thereof. As mentioned above, two igniters are fixed to theinitiator collar 13 so as to form a single member by providing twoigniters 12 a and 12 b in one initiator collar 13, thereby facilitatingan assembly to the gas generator. In particular, in the gas generatorillustrated in this drawing, since the initiator collar 13 is formed ina size capable of being inserted into the inner cylindrical member 4,the igniters are easily and securely fixed by crimpig the lower end ofthe inner cylindrical member 4 so as to fix the initiator collar afterinserting the initiator collar 13 provided with two igniters 12 a and 12b into the inner cylinder 4. Further, when arranging two igniters (12 a,12 b) in the initiator collar 13, a direction of each igniter can beeasily controlled.

[0071] In this embodiment, a substantially cylindrical separatingcylinder 14 is arranged in a space between the initiator collar 13 andthe partition wall 7 so as to surround one igniter 12 b (hereinafter,refer to as “a second igniter”), a first transfer charge accommodatingchamber 15 a defined in the outer side of thereof and a second transfercharge accommodating chamber 15 b are defined in the inner side thereofrespectively, and the igniter and the transfer charge constituting theignition means together with the igniters are stored in eachaccommodating chambers. As a result, transfer charges (16 a, 16 b)constituting the ignition means together with the igniters are securelypartitioned into the respective igniters (12 a, 12 b). When the transfercharge 16 a in the first transfer charge accommodating chamber 15 a isburnt, the seal tape 18 closing the flame-transferring hole 17 providedon the cylindrical member 4 is ruptured, by whereby the first transfercharge accommodating chamber 15 a communicates the first combustionchamber 5 a. And when the transfer charge 16 b in the second transfercharge accommodating chamber 15 b is burnt, the seal tape 20 closing theflame-transferring hole 19 provided on the partition wall 7 is ruptured,by whereby the second transfer charge accommodating chamber 15 bcommunicates the second combustion chamber 5 b. Accordingly, in this gasgenerator, at activation, a flame generated, when the first igniter 12 ais ignited (activated), ignites and burns the transfer charge 16 a inthe accommodating chamber 15 a and then, the flame thereof passesthrough the flame-transferring hole 17 formed in the inner cylindricalmember 4 and ignites and burns a gas generating agent 9 a with sevenholes stored in the first combustion chamber 5 a positioned in theradial direction of the chamber 15 a. And the second igniter 12 bignites and burns the second transfer charge 16 b stored in theaccommodating chamber 15 b and the flame thereof passes through theflame-transferring hole 19 provided in the axial direction of theaccommodating chamber 15 b and ignites and burns a gas generating agent9 b with a single hole stored in the second combustion chamber 5 bdisposed on an extension thereof. The combustion gas generated in thesecond combustion chamber 9 b passes through the through hole 10provided in the diffuser shell side 1 of the inner cylindrical member 4and flows into the first combustion chamber 5 a. Particularly, in thegas generator shown in FIG. 1, the separating cylinder 14 arrangedbetween the initiator collar and the partition wall is arranged so thata hole portions 21 corresponding to an outer shape of the separatingcylinder 14 are provided on the lower surface of the partition wall 7and the upper surface of the initiator collar 13, and the upper end andthe lower end of the separating cylinder 14 are fitted into therespective hole portions. By arranging the separating cylinder 14 inthis manner, a flame of the transfer charge generated in one of thetransfer charge combustion chambers does not directly burn the transfercharge in the other transfer charge accommodating chamber, and the gasgenerating agents stored in two combustion chambers are respectivelyignited and burnt by the flame generated by the combustion of thetransfer charges in the different sections. Namely, in general, when thetransfer charge burns in the separating cylinder 14 (that is, in thesecond transfer charge accommodating chamber), a pressure of the gasgenerated by the combustion serves so as to expand the separatingcylinder in the radial direction, however, by arranging the separatingcylinder the upper and lower end portions of the separating cylinder aresecurely supported to peripheral walls of the hole portions where therespective portions are fitted, so that, in comparison with the case ofsimply interposing the separating cylinder between the partition walland the initiator collar, leaking of the combustion gas and the flame ofthe transfer charge can be prevented securely.

[0072] Further, a coolant/filter 22 for purifying and cooling thecombustion gas generated by the combustion of the gas generating agents(9 a, 9 b) is disposed in the housing 3, an inner peripheral surface inthe diffuser shell 1 side thereof is covered with a short passpreventing member 23 so that the combustion gas does not pass between anend surface of the coolant/filter 22 and a ceiling portion inner surface28 of the diffuser shell 1. An outer layer 24 for preventing the filter22 from expanding outwardly due to passing of the combustion gas or thelike is arranged on the outer side the coolant/filter 22. The outerlayer 24 is, for example, formed by using a layered wire mesh body, andin addition, may be formed by using a porous cylindrical member having aplurality of through holes on a peripheral wall surface or a belt-likesuppressing layer obtained by forming a belt-like member with apredetermined width into an annular shape. A gap 25 is further formed onthe outer side of the outer layer 24 so that the combustion gas can passthrough the entire surface of the filter 22.

[0073] The gas generator of the present invention is characterized in astructure of the gas discharge port formed in the diffuser shell 1and/or the seal tape for closing the gas discharge port. A peripheralwall portion of the diffuser shell 1 of the gas generator shown in FIG.1 is provided with two kinds of gas—discharge ports 26 a and 26 b havingdifferent diameters, and the number of the respective ports can be setequal. In this case, since the diameter of the gas discharge port 26 ais larger than that of the gas discharge port 26 b and the number of therespective ports are the same, the total opening area of the gasdischarge port 26 a is greater than that of the gas discharge port 26 b.In the present embodiment, the diameter of the gas discharge port 26 ais φ3.0 mm, the number of holes thereof is 10, the diameter of the gasdischarge port 26 b is φ2 mm, and the number of holes thereof is 10.Seal tapes 27 are pasted to the gas discharge ports 26 a and 26 b on theinner peripheral surface of the peripheral wall of the diffuser shell 1in order to protect the gas generating agent against influence ofenvironment such as moisture outside the housing. Preferably, the sealtape 27 has a width well enough for closing two kinds of gas dischargeports together which are arranged in the axial direction of the gasgenerator and the tape 27 has an excessive margin of 2 to 3 mm from theupper or lower end of the gas discharge ports 26 a and 26 b to the upperor lower end of the seal tape. The seal tape comprises an aluminum seallayer having thickness of 20 μm to 200 μm and an bonding layer oradhesive layer having thickness of 5 to 100 μm. However, as long as thetape can exhibit the desired effect, a kind or structure of the sealtape is not limited. The present embodiment uses a seal tape comprisingan aluminum seal layer having thickness of 50 μm and an bonding layer oradhesive layer having thickness of 50 μm. The gas discharge ports 26 aand 26 b are arranged in the axial direction of the housing of the gasgenerator in the present embodiment, but the gas discharge ports may bearranged alternately and circumferentially in the peripheral wall of thediffuser shell in order to obtain the effect of the present invention.By means of the combination of the gas discharge ports and the seal tapedescribed above, the pressure for breaking the seal tape is adjusted attwo stages.

[0074] An opening of diameter 3 mm has an area of 0.71 cm, an opening ofdiameter 2 mm has an area of 0.31 cm², and when there are 10 holes, thetotal opening area is 10.2 cm² With respect to openings being next toeach other in opening diameter, a ratio of the opening diameters is 1.5.A ratio of opening area is 2.29/1.

[0075] When the gas generator is activated in this structure, forexample, when an igniter for igniting the single-hole gas generatingagent of the combustion chamber 5 b is activated after 3 mm/sec fromenergization of the igniter for igniting the seven hole gas generatingagent in the combustion chamber 5 a, the opening area (the diameter andthe number of holes) of the discharge ports 26 a is correlated with asurface area of combustion of the gas generating agent in the combustionchamber 5 a, and further the opening area (the diameter and the numberof holes) of the discharge ports 26 b is correlated with a surface areaof combustion of the gas generating agent in the combustion chamber 5 b.Conventionally, since the discharge ports have one kind of diameter, itwas only possible that the opening area is correlated with the surfacearea of the gas generating agent in the combustion chamber 5 a or withthe surface of all the gas generating agent of the combustion chambers 5a and 5 b. In the former case, the condition is optimal when the gasgenerating agent in the combustion chamber 5 a is burnt, but when thegas generating agent in the combustion chamber 5 b is subsequently burntor when the gas generating agents in both combustion chambers 5 a and 5b are burnt, the combustion pressure may become high, and the gasgenerator may excessively output. Further, in the latter case, when onlythe gas generating agent in the combustion chamber 5 a is first burnt,the output becomes too slow on the contrary, and therefore, sufficientrestraining performance at the initial developing stage of the air bagcan hardly obtained.

[0076] According to the present invention, as shown in the presentembodiment, two kinds of discharge ports having different opening areasare provided, the area thereof is correlated with the surface area ofthe gas generating agent of each of the combustion chambers, therebyobtaining optimal development of the air bag irrespective of ignitiontiming of the gas generating agent. Although the number of kinds of theopening area of the gas discharge port is two, it is also possible tosuppress the difference in output performance due to environmenttemperature by further increasing the kinds and adjusting the breakingpressure of the seal tape at multiple stages. Such an effect of thepresent invention can be confirmed also by the following tank combustiontest.

[0077] <Tank combustion test>

[0078] A gas generator for the air bag is fixed in a SUS (stainlesssteel) tank with an inner volume of 60 litter and is connected to anouter ignition electric circuit after sealing the tank at a roomtemperature. With setting a time when an ignition electric circuitswitch is turned on (an ignition electric current is applied) to 0, apressure increase change inside the tank is measured by a pressuretransducer independently placed in the tank for a time between 0 and 200milliseconds. Each of the measured data is finally set to a tankpressure/time curve by a computer process, and a curve estimating aperformance of a gas generating molded article (hereinafter, refer to as“a tank curve”) is obtained. After finishing the combustion, the gas inthe tank is partly taken out and may be applied to a gas analysis forCo, NOx, etc.

[0079] In the gas generator constituted in the above manner, when thefirst igniter 12 a disposed in the outer side the separating cylinder 14which is inside the ignition means accommodating chamber 8 and isactivated, the transfer charge 16 a stored in the first transfer chargeaccommodating chamber 15 a is ignited and burnt, and the flame thereofpasses through the flame-transferring hole 17 in the inner cylindricalmember 4 and burns the porous cylindrical first gas generating agent 9 awith seven holes and stored in the first combustion chamber 5 a. Andwhen the second igniter 12 b surrounded by the separating cylinder 14 isactivated, the transfer charge 16 b stored in the second transfer chargeaccommodating chamber 15 b is ignited and burnt, and the flame thereofignites and burns the single-hole cylindrical second gas generatingagent 9 b stored in the second combustion chamber 5 b. As a result, anoutput's forms (an actuation performance) of the gas generator can beoptionally adjusted by adjusting the ignition timings of two igniters 12a and 12 b such as activating the second igniter after the activation ofthe first igniter or simultaneously activating the first igniter and thesecond igniter. And therefore, under various kinds of circumstances suchas a speed of a vehicle and an environmental temperature at a time ofcollision, it is possible to make a inflation of the air bag in the airbag apparatus mentioned below most suitable. Particularly, in the gasgenerator shown in this drawing, the respective combustion chambers (5a, 5 b) adopt the gas generating agents (9 a, 9 b) to provide differentshapes from each other, respectively, and the porous cylindrical firstgas generating agent 9 a and the single-hole cylindrical second gasgenerating agent 9 b are respectively stored in the first combustionchamber 5 a and the second combustion chamber 5 b. Further, the amountof the gas generating agent stored in each combustion chamber (5 a, 5 b)is different, and the gas generating agents (9 a, 9 b) at an amount of35 g and 6 g are stored respectively in the first combustion chamber 5 aand the second combustion chamber 5 b. Consequently, in this gasgenerator, the output's forms can be adjusted more precisely. Naturally,a shape, a composition, a composition ratio, an amount, etc. of the gasgenerating agent may be changed to obtain the desired output's forms.

[0080] According to the present invention, the internal pressure at thetime of activation of the gas generator can be equalized and thecombustion performance can be stabilized by the combination of the twoor more igniters and two kinds or more of gas discharge ports describedabove.

[0081] The gas generator shown in FIG. 2 has the same structure as thatshown in FIG. 1 except that structures of the gas discharge portprovided in the diffuser shell of the housing and of the seal tape forclosing the gas discharge port are changed, the same members as thoseshown in FIG. 1 are designated with the same symbols, and explanationthereof is omitted. In other words, FIG. 2 shows an embodiment in whichin order to adjust the pressure for breaking the seal tape at twostages, the opening areas of the gas discharge ports (the diameters andthe number of holes) are the same but the thickness of the seal tapesare changed. The gas generator includes twenty openings 26 a and 26 beach having a diameter of 3 mm which are closed with fourteen seal tapes27 a comprising aluminum layer of 80 μ and bonding layer of 50 μ, andsix seal tapes 27 b comprising aluminum layer of 160 μ and adhesivelayer of 50 μ. In this gas generator, a ratio of thickness is 1.61/1,and an opening area is 70/30. In this case, the gas discharge ports 26 aand the gas discharge ports 26 b are arranged vertically in the axialdirection of the housing, and the seal tape 27 b closing the gasdischarge port 26 b is thicker than the seal tape 27 a closing the gasdischarge port 26 a. However, the thickness of the seal tape iscontrolled to adjust the output performance (activating performance) ofthe gas generator, and the internal pressure in the housing at the timeof combustion of the gas generating agent is adjusted by the openingarea of the gas discharge port. That is, the seal tape does notinfluence the maximum combustion internal pressure. The opening areas ofthe gas discharge ports 26 a and 26 b (the diameters and the number ofholes) are the same. In this case, for example, when the gas generatingagent 9 a in the combustion chamber 5 a is burnt, the opening area ofthe gas discharge port 26 a and the thickness of the seal tape 27 a areadjusted so that all seal tapes 27 a covering the gas discharge ports 26a are broken. When the gas generating agent 9 b in the combustionchamber 5 b is subsequently burnt, or when the gas generating agents 9 aand 9 b in the combustion chambers 5 a and 5 b are simultaneously burnt,higher combustion internal pressure is generated. Therefore, at thattime, the thicker seal tape 27 b is pasted to the gas discharge port 26b so that the seal tapes 27 a and 27 b covering all the gas dischargeports 26 a and 26 b are broken. In other words, the thickness of theseal tape 27 a of the gas discharge port 26 a is adjusted so that theseal tape 27 a is broken only by the combustion of the gas generatingagent 9 a in the combustion chamber 5 a and thus, the seal tape 27 b ofthe gas discharge port 26 b cannot be broken. For this reason, since thesurface area of the gas generating agent in the combustion chamber 5 ais correlated only with the opening area of the gas discharge port 26 a,the optimal combustion can be obtained. Thereafter, if the gasgenerating agent 9 b in the combustion chamber 5 b is burnt atintervals, or when the gas generating agents 9 a and 9 b in both thecombustion chambers are simultaneously burnt, further higher combustionpressure is generated. Therefore, the seal tape 27 b of the gasdischarge port 26 b is also broken to suppress increase of the internalpressure, and the air bag can be developed in the optimal mannerirrespective of ignition timing. In this case also, as described withreference to FIG. 1, material and structure of the seal tape, andarrangement of the gas discharge port are not a limiting element forobtaining the effect of the object, and arbitrary manner can beemployed. Further, by changing the thickness at multiple stages, the gasgenerator is less influenced by environment temperature and the like.

[0082] Although opening areas of the gas discharge ports and thethickness of the seal tape are changed into several kinds in the twoembodiments shown in FIGS. 1 and 2, both of them can also be adjusted.

[0083] Embodiment 2

[0084]FIG. 3 is a vertical cross sectional view which shows the otherembodiment of a gas generator for an air bag according to the presentinvention. This gas generator is structured such as to be particularlysuitable for being arranged in passenger sides.

[0085] The gas generator shown in this drawing has in the housing 103formed into a cylindrical shape having an axial core length longer thanan outermost diameter and having a plurality of gas discharge ports on aperipheral wall thereof, and an ignition means to be actuated on animpact, gas generating agents (9 a, 9 b) which is to be ignited andburnt by the ignition means and generate a combustion gas for inflatingthe air bag and a coolant/filter 122 for cooling and/or purifying thecombustion gas generated by the combustion of the gas generating agents.Then, two combustion chambers (105 a, 105 b) provided in the housing 103are concentrically provided so as to be adjacent to each other to anaxial direction of the housing 103, and a communicating hole 110 whichallows communication between the combustion chambers 105 a and 105 b isprovided.

[0086] The gas generator shown in the present embodiment is formed in along shape in the axial direction since the housing is formed in a longcylindrical shape in the axial direction. The gas generator formed inthis shape can be a gas generator having a simple structure and easilymanufactured while the output of the gas generator and the timing forincreasing the output can be optionally adjusted by concentricallyproviding two combustion chambers 105 a and 105 b so as to be adjacentto each other and making both the combustion chambers communicate witheach other.

[0087] Then, the ignition means comprises two or more igniters to beactivated on an impact and the respective igniters (12 a, 12 b) areprovided in one initiator collar 113 so as to be parallel to each other,and thereby an assembly thereof can be easily performed. Further, theigniters (12 a, 12 b) fixed in one initiator collar 113 and stored inthe housing is arranged eccentrically with respect to an axis of thehousing.

[0088] Further, a coolant/filter 122 formed in a substantiallycylindrical shape is arranged in the housing 103 so as to oppose to ahousing inner peripheral surface on which a plurality of gas dischargeports 126 a and 126 b are formed, and a predetermined gap 125 isobtained between the filter 122 and the housing inner periphery. Thefirst combustion chamber 105 a is defined so as to be adjacent to aspace in which the coolant/filter 122 is installed, and the ignitionmeans including two igniters (12 a, 12 b) is concentrically arranged soas to be adjacent to the first combustion chamber 105 a. Then, since theannular second combustion chamber 105 b is defined in the radialdirection of the ignition means, the first combustion chamber 105 a andthe second combustion chamber 105 b are provided so as to be adjacent toeach other in the axial direction of the housing 103. The different gasgenerating agents (9 a, 9 b) are respectively charged in the first andsecond combustion chambers, and in the gas generator shown in thisdrawing, the porous cylindrical first gas generating agent 9 a and thesingle-hole cylindrical second gas generating agent 9 b are respectivelystored in the first combustion chamber 105 a and the second combustionchamber 105 b.

[0089] The above ignition means comprises the transfer charges which areto be ignited and burnt according to the activation of the igniters (12a, 12 b) and ignites the gas generating agents (105 a, 105 b) by theflame thereof, and the transfer charges are partitioned for each igniterand independently ignited and burnt at each of the igniters. A spacewhere the transfer charge partitioned for each igniter is stored, isdefined by a cylindrical member, a first transfer charge accommodatingchamber 115 a where a first transfer charge 116 a is stored communicateswith the first combustion chamber 105 a by a flame-transferring hole 119on a partition wall 107 arranged between the ignition means and thefirst combustion chamber 105 a, and a second transfer chargeaccommodating chamber 115 b where a second transfer charge 116 b isstored communicates with the second combustion chamber 105 b by aflame-transferring hole 117 formed on the cylinder member 104 whichdefines the accommodating chamber 115 b. Then, the first combustionchamber 105 a and the second combustion chamber can be communicates witheach other by the through hole 110.

[0090] In the gas generator shown in the drawing, when the first igniter12 a is activated, the transfer charge 116 a in the first transfercharge accommodating chamber 115 a is ignited and burnt, and the flamethereof passes through the flame-transferring hole 119 in the partitionwall member 107 and ignites and burns the gas generating agent 9 astored in the first combustion chamber 105 a so as to generate thecombustion gas. This combustion gas is purified and cooled while passingthrough the coolant/filter 122 and is discharged from a gas dischargeport. On the other hand, when the second igniter 12 b is actuated, thetransfer charge 116 b in the second transfer charge accommodatingchamber 115 b is ignited and burnt, and the flame thereof ignites andburns the gas generating agent 9 b in the second combustion chamber 105b. The combustion gas generated in the second combustion chamber 105 bpasses in the first combustion chamber 105 a through the through hole110 in the partition wall 107, is purified and cooled while passingthrough the coolant/filter 122 and then, is discharged from the gasdischarge port 126.

[0091] Further, also in the gas generator shown in this figure, thethrough hole 110 for bringing the first and second combustion chambersinto communication with each other is closed by the seal tape 111 whichis to be broken by the combustion of the gas generating agent in thesecond combustion chamber exclusively. In the present embodiment also,like the gas generator shown in FIG. 1, a large diameter gas dischargeport 126 a and a small diameter gas discharge port 126 b are provided,and they are closed by the seal tapes 127. That is, in the embodimentshown in FIG. 3, like the embodiment shown in FIG. 1, the thicknesses ofthe seal tapes are constant, and two kinds of the opening areas of thegas discharge ports are provided, thereby making it possible to controlthe breaking pressure of the seal tape and to always adjust the outputin the optimal manner irrespective of combustion timing of the gasgenerating agents 9 a and 9 b in the combustion chambers 105 a and 105b. The gas discharge ports are formed in the peripheral wall of thecylindrical housing, the surface area of the gas generating agent 9 a inthe combustion chamber 105 a is correlated with the opening area of thegas discharge port 126 a, and the surface area of the gas generatingagent 9 b in the combustion chamber 105 b is correlated with the openingarea of the gas discharge port 126 b. Since the operational principle isthe same as that shown in FIG. 1, detailed explanation thereof isomitted.

[0092] Further, a communicating hole 161 communicating both chambers isprovided in a sectioning member 160 which partitions the firstcombustion chamber 105 b and the space where the coolant/filter 122 isinstalled, the combustion gas generated in the first and secondcombustion chambers (105 a, 105 b) reaches the space installing thecoolant/filter 122 through the communicating hole 161. According to thisembodiment, a communicating hole 161 having substantially the same sizeas an inner diameter of the coolant/filter 122 is formed in thesectioning member 160. Then, a wire mesh 162 is placed in thecommunicating hole 161 so that the gas generating agent 9 a in the firstcombustion chamber 105 a does not move to a side of the space where thecoolant/filter 122 is installed, at a time of the combustion. Any kindsof wire mesh can be used for this wire mesh 162 as long as it does nothave a mesh size which can prevent the first gas generating agent 9 afrom moving during the combustion and does not have a draft resistancesuch as to control the combustion performance.

[0093] As mentioned above, also in the gas generator according to thisembodiment, the gas generating agents (9 a, 9 b) stored in therespective combustion chambers (105 a, 105 b) are independently ignitedand burnt by adjusting the activation timing of two igniters (12 a, 12b), so that the output's forms (the actuation performance) of the gasgenerator can be optionally adjusted. Consequently, in variouscircumstances such as the speed of the vehicle at a time of collision,an environmental temperature, it is possible to make it most suitable toinflate the air bag in the case of using an air bag apparatus mentionedbelow.

[0094] In FIG. 3, two combustion chambers provided in the housing can beprovided so as to be adjacent to each other in the axial direction andthe radial direction of the housing. Concretely, in the gas generatorshown in FIG. 3, a second combustion chamber 105 b is extended in theaxial direction of the housing by bending the partition wall 107 whichdefines a first combustion chamber 105 a and ignition means and a secondcombustion chamber 105 b in the axial direction, thereafter forming aend thereof into a flange shape and placing it in contact with an innerperiphery of the housing. As a result, in the gas generator shown inFIG. 3, the second combustion chamber is extended in the axialdirection, that is, extended to the first combustion chamber side, bywhereby the first combustion chamber and the second combustion chamberare adjacent to each other in the axial direction and the radialdirection of the housing. In the gas generator shown in FIG. 3, thevolume of the second combustion chamber can be made larger, which isadvantageous in the case that the second gas generating is used in largeamount.

[0095]FIG. 4 is a vertical cross sectional view of an embodiment of agas generator for restraining an occupant on a passenger side as in FIG.3, and shows an embodiment in which opening areas of the discharge portsare constant as shown in FIG. 2, and the thicknesses of the seal tapesare changed so as to adjust the breaking pressure. That is, the gasdischarge port 126 a and the gas discharge port 126 b are arrangedvertically in the axial direction of the housing, and the seal tape 127b for closing the gas discharge port 126 b is thicker than the seal tape127 a for closing the gas discharge port 126 a. The opening areas (thediameters and the number of holes) of the gas discharge ports 126 a and126 b are the same. In the activation of the gas generator shown in FIG.4, the same members those shown in FIG. 3 are designated with the samenumerals, and explanation thereof is omitted. Since the structure andoperation of the gas discharge ports and the seal tapes are the same asthose shown in FIG. 2, explanation of the operation thereof is omitted.

[0096] Also in the case of the gas generator for restraining theoccupant on the passenger side shown in FIGS. 3 and 4, delicateadjustment to reduce the influence by the outside temperature can berealized by further increasing the kinds of opening areas of the gasdischarge ports and the kinds of the thicknesses of the seal tapes.Naturally, the opening areas of the gas discharge ports and thethicknesses of the seal tapes may be combined simultaneously.

[0097] Embodiment 3

[0098]FIG. 5 is a vertical cross sectional view showing a gas generatorfor an air bag of the present invention in another embodiment. The gasgenerator shown in this embodiment also has a structure suitable forbeing disposed in the driver side like the gas generators shown in FIGS.1 and 2.

[0099] The gas generator shown in FIG. 5 has the same structure as thatshown in FIG. 1 except a structure of a partition wall which defines acylindrical member into a second combustion chamber and an ignitionmeans accommodating chamber. Therefore, the same members as those shownin FIG. 1 are designated with the same numerals, and explanation thereofis omitted.

[0100] Particularly in the gas generator shown in this figure, thepartition wall 307 in a substantially flat curricular shape whichpartitions the interior of the inner cylinder into the second combustionchamber and the ignition means accommodating chamber is, as shown in anexploded perspective view in FIG. 6, constituted by a sectioningcircular member 350 engaged with the stepped notch portion 306 of theinner cylindrical member 304 and a seal cup member 360 engaged with thesectioning circular member 350.

[0101] The sectioning circular member 350 is formed in a substantiallyflat circular shape, and has an opening portion 351 inwardly fitting atransfer charge accommodating portion 361 of a seal cup member 360mentioned below, a circular hole portion 352 obtained by scraping out abottom surface in a circular shape and storing an upper portion of anigniter 312 b, and a second flame-transferring hole 319 extending andpierced through a substantially center of the circular hole portion.Further, the seal cup member 360 has a cylindrical transfer chargeaccommodating portion 361 fitted into the opening portion 351 of thesectioning circular member 350 and protruding into the second combustionchamber 305 b, and a cylindrical igniter receiving port 362 formed at aposition opposing to the circular hole portion 352 of the sectioningcircular member 350 and extending to a side opposite to the transfercharge accommodating portion 361. A first transfer charge 316 a isstored inside the transfer charge accommodating portion 361, and asecond igniter 312 b is inwardly fitted to the igniter receiving port362. The sectioning circular member 350 and the seal cup member 360 areengaged with each other by fitting the transfer charge accommodatingportion 361 of the seal cup member 360 into the opening portion 351 ofthe sectioning circular member 350, and an upper portion of the secondigniter 312 b inwardly fitted to the igniter receiving port 362 exposesinto the circular hole portion 352 of the sectioning circular member350. The partition wall 307 constituted by the sectioning circularmember 350 and the seal cup member 360 is, as shown in FIG. 5, engagedwith the stepped notch portion 306 formed on the inner peripheralsurface of the inner cylindrical member 304. That is, the peripheraledge of the sectioning circular member 350 is supported to the steppednotch portion 306, and the seal cup member 360 is supported in contactwith the sectioning circular member 350. Further, the peripheral edge ofthe seal cup member 360 is formed by being bent in the same direction asthat of the igniter receiving port 362, and a bent portion 363 is fittedinto a groove 364 provided on the inner peripheral surface of the innercylindrical member 304. Accordingly, the sectioning circular member 350is supported by the seal cup member 360 and is prevented from moving inthe axial direction of the housing 3. Further, the partition wall 307(i.e. the seal cup member 360) and the inner cylindrical member 304 areengaged with each other with no gap by fitting the bent portion 363 inthe peripheral edge of the seal cup member 360 into the groove 364 onthe inner peripheral surface of the inner cylindrical member 304.Accordingly, in the inner cylindrical member 304, the ignition meansaccommodating chamber 308 provided in the closure shell side 2 and thesecond combustion chamber 305 b provided in the diffuser shell side 1are securely partitioned by an ignition means sealing structurecomprising a combination of the seal cup member 360 and the groove 364.

[0102] The igniter receiving port 362 formed in the seal cup member 360is structured such that a skirt portion thereof spreads like a fan, andan O-ring 381 is arranged in an inner side thereof, that is, betweenthis and the second igniter 312 b stored in the storing port 362, andsealing between the receiving port 362 and the second igniter 312 b isperformed. And since the O-ring 381 is also press-contacted to anigniter fixing member 382 which fixes two igniters 312 a and 312 b tothe single initiator collar, the second igniter 312 b is arranged in aspace defined by the circular hole portion 352 of the sectioningcircular member, the igniter receiving port 362 of the seal cup member,the O-ring 381 and the igniter fixing member 382. When the seal tape 320closing the second flame-transferring hole 319 formed in the circularhole portion 352 of the sectioning circular member 350 is ruptured bythe activation of the second igniter 312 b, the inner portion of thedefined space communicates with the second combustion chamber 305 b.Then, the first igniter 312 a and the second igniter 312 b are securelyseparated by a seal structure comprising the skirt portion of theigniter receiving port 362, the O-ring 381 and the igniter fixing member382 (hereinafter, referred as “an igniter seal structure”). Accordingly,the flame generated by the activation of any igniter does not directlyflow into the space where the other igniter is stored.

[0103] The igniter fixing member 382 is formed in a shape which coversan upper surface of the initiator collar 313, and has a hole portion 384passing through the upper portion of each igniter and supporting ashoulder portion 383. Two igniters 312 a and 312 b arranged in theinitiator collar 313 are fixed to the igniter fixing member 382outwardly fitted to the initiator collar 313. By using the above igniterfixing member 382, two igniters 312 a and 312 b can be easily assembledto the initiator collar 313. In the gas generator shown in thisembodiment, the first igniter 312 a and the second igniter 312 b areformed in different sizes, and the outputs thereof are different,however, the igniters having the same output may be used.

[0104] In the gas generator shown in this drawing also, like the gasgenerator shown in FIG. 1, opening diameters and/or opening areas of theplurality of gas discharge ports (26 a, 26 b) formed in the housing arecontrolled by arranging two kinds or more. As a result, in this gasgenerator for the air bag, a difference in the maximum internalpressures of the housing at activation of the respective ignition meanscan be suppressed, the internal pressure at the time of activation ofthe gas generator can be equalized, and the combustion performance canbe stabilized. In the gas generator in this embodiment also, like thegas generator shown in FIG. 2, the opening areas of the gas dischargeports are constant and the thicknesses of the sealing means such as theseal tapes 27 are changed to adjust the breaking pressure, and thereby,a difference in the maximum internal pressures of the housing atactivation of the respective ignition means can be suppressed. Further,it is naturally possible to concurrently use the control of the openingdiameters and/or opening areas of the gas discharge ports and thecontrol of the thicknesses of the sealing means.

[0105] Embodiment 4

[0106]FIG. 7 is a vertical cross sectional view which shows a gasgenerator for an air bag according to the other embodiment of thepresent invention. The gas generator shown in this embodiment also has astructure being particularly suitable for being arranged in a driverside in the same manner as that of the gas generator shown in theEmbodiments 1 and 3 mentioned above.

[0107] In particular, the gas generator shown in this embodiment ischaracterized by an arrangement of two combustion chambers provided inthe housing and a forming method.

[0108] Also in the present embodiment, a gas discharge port 410 formedin a diffuser shell 401 has two kinds of gas discharge ports 410 a and410 b having different diameters, and these are closed by a seal tape429 for protecting a gas generating agent 452 from an influence of anenvironment such as a humidity outside the housing. By providing twokinds of gas discharge ports 410 a and 410 b having different innerdiameters (and opening areas), a combustion internal pressure in thehousing 403 at an actuation can be equalized (stabilizing of acombustion performance). Since this actuation was already described inthe Embodiment 1, it will be omitted here. A structure of the gasgenerator according to the present embodiment will be described below.

[0109] That is, in the gas generator shown in this embodiment, in acylindrical housing 403 obtained by joining a diffuser shell 401 havinga plurality of gas discharge ports 410 and a closure shell 402 forforming an inner storing space together with the diffuser shell 401 andapplying a friction welding to these shells, a cylindrical inner shell404 in a capsule-like shape having a circle in the horizontal crosssection and a closed upper end is arranged and fixed eccentrically withrespect to the center axis of the housing, thereby forming a firstcombustion chamber 450 is formed in an outer side thereof and forming asecond combustion chamber 460 in an inner side thereof.

[0110] A eccentric degree of the inner shell 404 arranged in the housing403 with respect to the housing 403 can be suitably changed according toa desired volume ratio of a combustion chamber and the like, and may bechanged according to a structure inside the housing 403, for example,whether or not a coolant/filter 425 exists. As an example, like the gasgenerator shown in this drawing, when the coolant/filter 425 is arrangedopposite to a peripheral wall surface of the housing 403, it is possibleto suitably select in a range between 10 and 75%. However, since thisrange can be changed due to a size of the igniters 451 and 461 and thelike, the range is only a measure of eccentricity of the inner shell 404in the gas generator shown in FIG. 7.

[0111] The inner shell 404 may be formed in various kinds of shapes suchas a rectangular shape, an oval shape and the like in a horizontal crosssection, in order to join easily to the closure shell 402, etc., it ispreferable to be formed in a circular shape. In other wards, thehorizontal cross sectional shape of the inner shell 404 has to be acircular shape when joining the inner shell 404 and the closure shell402 by a friction welding, and also when joining by a laser welding, itis necessary to keep an emitting distance of the laser constant.

[0112] As mentioned above, in this embodiment, the first combustionchamber 450 and the second combustion chamber 460 are defined by theinner shell 404. That is, the first combustion chamber 450 is providedon the outer side of the inner shell 404, and the second combustionchamber 460 is provided on the inner side of the inner shell 404. Avolume ratio between the first combustion chamber 450 and the secondcombustion chamber 460 (a volume of the first combustion chamber avolume of the second combustion chamber) is set to 3.3:1 in the presentembodiment, and it can also be suitably selected in a range of 97:1 to1:1.1. However, also with respect to the volume ratio, the selectedrange can be suitably changed due to a size of the igniters (451, 461)and a shape of the gas generating agents (452, 462). Accordingly, theabove range shows a range which can be selected in the structure of thegas generator shown in this drawing.

[0113] As mentioned above, the gas generating agents (452, 462) arerespectively stored in the second combustion chamber 460 and the firstcombustion chamber 450 which are partitioned by the inner shell 404. Thefirst gas generating agent 452 is stored in the first combustion chamber450 and the second gas generating agent 462 is stored in the secondcombustion chamber 460, respectively. In the present embodiment, thefirst gas generating agent 452 and the second gas generating agent 462have the same shape or the like. The gas generating agents differentfrom each other in at least one of a burning rate, a composition, acomposition ratio and an amount can be stored in the respectivecombustion chambers.

[0114] The inner shell 404 which defines the first combustion chamber450 and the second combustion chamber 460 is arranged eccentrically withrespect to the center axis of the housing 403, and the second combustionchamber 460 provided inside the inner shell 404 is eccentric withrespect to the housing 403. The igniters are respectively arranged inthe first combustion chamber 450 and the second combustion chamber 460,the second igniter 461 arranged in the second combustion chamber 460 isdisposed in the center of the second combustion chamber 460 which iseccentric with respect to the center axis of the housing 403. Therefore,a flame generated by an activation of the igniter 461 can uniformlyburns the second gas generating agent 462. And the second igniter 461and the first igniter 451 disposed in the first combustion chamber 450are both arranged eccentrically with respect to the center axis of thehousing 403. As mentioned above, by arranging eccentrically the firstand second igniters as well as the inner shell 404 with respect to thecenter axis of the housing 403, a range of a difference in the volumeratio of the first and second combustion chambers can be made larger,and the size of the housing 403 in a diametrical direction can berestricted as much as possible.

[0115] Among the igniters arranged in the respective combustionchambers, the igniter 451 arranged in the first combustion chamber 450has a transfer charge 408 arranged in a peripheral and upper directionsthereof. For convenience at assembling the gas generator, or in order toprevent the transfer charge 408 from being scattered in the firstcombustion chamber 450 due to the impact and the vibration applied atmounting on the vehicle, and to prevent an ignition performance to thefirst gas generating agent 452 form being slipped, the transfer charge408 is stored in a transfer charge container 426. The transfer chargecontainer 426 is easily broken due to the combustion of the transfercharge 408 arranged therein and formed by an aluminum having a thickness(for example, about 200 μm) so as to transfer the flame to the peripherythereof. On the other hand, a transfer charge like the one arranged inthe first combustion chamber 450 is not necessarily required in thesecond combustion chamber 460. This is because the second gas generatingagent 462 is ignited more easily, than the first gas generating agent452, and the pressure of the second combustion chamber is increasing ina sealed state until the breaking member 407 for sealing a hole 406 ofthe below-described inner shell 404 is ruptured. The breaking member 407is not ruptured even when the internal pressure of the combustionchamber 450 increases due to the combustion of the first gas generatingagent 452 but it is ruptured when the internal pressure of the secondcombustion chamber 460 increases more than that of the first combustionchamber 450. However, the transfer charge can be used as required.

[0116] A cylindrical member 436 is placed in the first combustionchamber 450 so as to surround an outer side in the radial direction ofthe first igniter 451 and the transfer charge 408 disposed above theigniter. The cylindrical member 436 is formed into a cylindrical shapeopen at both upper and lower ends, one end portion thereof is outwardlyfitted to an outer periphery of a portion fixed with the igniter 451 sothat no gap is formed. And the other end portion is inserted to besupported by a retainer 411 disposed near an inner surface of a ceilingportion of the diffuser shell 401 so as to be fixed to a predeterminedportion. A plurality of flame-transferring holes 437 are formed on aperipheral wall of the cylindrical member 436, and the flame generatedby the combustion of the transfer charge 408 is injected from theflame-transferring hole 437 so as to ignite and burn the first gasgenerating agent 452 disposed in the outer side of the cylindricalmember. It is preferable that the cylindrical member 436 is made of thesame material as that of the housing 403.

[0117] In particular, in the gas generator shown in this embodiment, thefirst combustion chamber 450 is formed into an annular shape similar toa crescent shape obtained by stamping an inner side of a circle roundly,as shown in a perspective plan view in FIG. 8, and the first gasgenerating agent 452 is placed therein. Accordingly, in the firstcombustion chamber 450, as is different from the second combustionchamber 460, a distance between the gas generating agent 452 and theigniter 451 is varied with a place for storing the gas generating agent452. Therefore, at a time of ignition of the igniter 451, the ignitionand the combustion of the first gas generating agent 452 are performedunevenly. Then, the flame-transferring hole 437 provided in a peripheralwall of the inner cylindrical member 436 restricts a direction thereofso as to lead the flame of the transfer charge 408 in a direction shownby an arrow in FIG. 8. Accordingly, it is possible to burn the gasgenerating agent 452 in a portion shaded by the second combustionchamber 460 (i.e. the inner shell 404) evenly. Further, in place of theinner cylindrical member 436, a injecting-direction restricting means(not shown) having holes formed in a direction shown by an arrow in FIG.8 can be used. The injecting-direction restricting means restricts thedirection of the injecting flame which is generated by the activation ofthe first ignition means (the igniter 451 and the transfer charge 408 inFIG. 7) for igniting the first gas generating agent 452, in order toeffectively burn the first gas generating agent 452. As theinjecting-direction restricting means, for example, a cup-like containerhaving one end portion closed by a cylinder member and in which a nozzlefor leading the flame of the ignition means in a desired direction (adirection shown by an arrow in FIG. 8) is provided on a peripheral wallportion. In this case, the injecting-direction restricting means is usedin a state of being mounted (covered) around the first ignition means.Also in the case of using the above injecting-direction restrictingmeans, it is preferable that the first ignition means arranged inside itcomprises the igniter and the transfer charge which is to be ignited andburnt by the activation of the igniter.

[0118] The inner shell 404 which defines the first combustion chamber450 and the second combustion chamber 460 is formed into a capsule shapeas mentioned above, and a plurality of opening portions 405 are formedon a peripheral wall thereof. The opening portion 405 is designed suchas to be opened only by the combustion of the second gas generatingagent 462 stored in the second combustion chamber 460 and is not openedby the combustion of the first gas generating agent 452 stored in thefirst combustion chamber 450. In the present embodiment, the openingportion 405 comprises a plurality of holes 406 provided on theperipheral wall of the inner shell 404 and the breaking member 407 forclosing the hole, and a stainless seal tape is used as the breakingmember 407. The breaking member 407 is designed such as to be broken,peeled, burnt or removed only by the combustion of the second gasgenerating agent 462 so as to open the hole 406 but not to be broken bythe combustion of the first gas generating agent 452.

[0119] The above inner shell 404 is fixed by connecting an open lowerportion 413 thereof to the closure shell 402. When the closure shell 402comprises the collar portion 402 a for fixing the igniter, the innershell 404 can be mounted to the collar portion 402 a. In the gasgenerator shown in FIG. 7, the closure shell 402 is formed such as tointegrally joint a circular collar portion having a size capable offixing two igniters on a bottom surface of the cylindrical shell portion402 b jointed to the diffuser shell 401, and the inner shell 404 isjointed to the collar portion 402 a. The collar portion 402 a can beintegrally formed on the bottom surface of the cylindrical shell portion402 b in a circular shape capable of being fixed at each igniter, andcan be integrally formed on the bottom surface of the cylindrical shellportion 402 b. In such a case, the inner shell 404 can be directlymounted on the bottom surface of the cylindrical shell portion 402 b inaddition to the collar portion 402 a of the closure shell.

[0120] In the present embodiment, a joint of the inner shell 404 and theclosure shell 402 can be performed by an uneven joint in addition to afriction welding, a cramping, a resistance welding and the like. Inparticular, in the case of joining the both by friction welding,preferably, it is performed in a state of fixing the closure shell 402.Accordingly, even when the axial cores of the inner shell 404 and theclosure shell 402 are not aligned to each other, a friction welding canbe performed stably. In other words, when friction welding is performedin a state of fixing the inner shell 404 and rotating the closure shell402, a center of gravity of the closure shell 402 is shifted from acenter of rotation and thereby a stable friction welding cannot beperformed. Therefore, in the present invention, friction welding isperformed in a state of fixing the closure shell 402 and rotating theinner shell 404. Further, at friction welding, it is preferable that theclosure shell 402 is positioned and fixed so as to always mount theinner shell 404 to a determined position. Accordingly, it is preferablethat a positioning means is suitably provided in the closure shell 402.A gas generating agent fixing member 414 is arranged in the inner shell404 in order to safely and smoothly perform a connection to the closureshell 402. The gas generating agent fixing member 414 is used in orderto prevent the gas generating agent 462 from directly contacting withthe inner shell 404 at a time of friction welding the inner shell 404 tothe closure shell 402 and to obtain a placing space for the igniter 461inside the space formed by the inner shell 404. When mounting the innershell 404 to the closure shell 402, in addition to the above frictionwelding, it is possible to mount by an uneven joint as well as acrimping, a resistance welding and the like. Also in this case, anassembly performance is improved by using the gas generating agentfixing member 414. The gas generating agent fixing member 414 adoptshere a canister made of aluminum and having a thickness which can beeasily broken by the combustion of the gas generating agent 462, as oneexample, and further, a suitable member capable of achieving the objectmentioned above (regardless a material, shape and the like) such as aporous member made of a wire mesh. Besides, when the above gasgenerating agent fixing member 414 is not used, it is possible to form alump of the gas generating agent obtained by forming a lump of thesingle-hole cylindrical gas generating agent 462 into the same shape asthe inner space of the inner shell 404 and place it in the inner shell404. In this case, the gas generating agent fixing member 414 may beomitted.

[0121] In the present embodiment, the collar portion 402 a of theclosure shell 402 is formed in a size capable of fixing two igniters 451and 461 horizontally. Accordingly, two igniters 451 and 461 arepreviously fixed to the collar portion 402 a by crimping, etc., andthen, this collar portion 402 is integrally formed with the cylindricalshell portion 402 b so as to form the closure shell 402, and thereby,two igniters 451 and 461 can be fixed to the closure shell 402. In thedrawing, the first igniter 451 and the second igniter 461 are describedin the same size, however, they may be structured such as to have adifferent output at each combustion chamber. Further, in thisembodiment, a cable 415 connected to each igniter 451 and 461 so as totransmit an activating signal is drawn out in the same direction.

[0122] A coolant/filter 425 is arranged in the housing 403 as filtermeans for purifying and cooling the combustion gas generated by thecombustion of the gas generating agent. The gases generated by thecombustion of the first and second gas generating agents both passthrough the coolant/filter 425. In order to prevent a short pass, thatis, to prevent the combustion gas from passing between an end surface ofthe coolant/filter 425 and an inner surface of the ceiling portion ofthe diffuser shell 401, the upper and lower inner peripheral surfaces ofthe coolant/filter 425 and the inner surface of the housing may becovered with a cylindrical short-pass preventing member having an inwardflange. In particular, in the gas generator shown in FIG. 7, aself-contracting type coolant/filter 425 tapers at both upper and lowerends outwardly in the radial direction. This self-contracting typecoolant/filter 425 will be described later with reference to FIG. 11.Also in this embodiment, in the same manner as the gas generator in FIG.11, a gap 428 which is a flow path for the combustion gas is formed onthe outer side the coolant/filter 425.

[0123] As mentioned above, in the gas generator shown in FIG. 7, theigniter (451, 461) and the inner shell 404 are arranged eccentricallywith respect to the housing 403. In the above gas generator, when thediffuser shell 401 and the closure shell 402 are joined by frictionwelding, joining the both the shells can be performed stably by fixingthe side of the closure shell 402 at the time of friction welding.Particularly, when inner shell 404 is directly mounted to the closureshell 402 by friction welding, as shown in FIG. 7, it is preferable thata flange portion 432 for mounting the gas generator to the module caseis provided in the side of the closure shell 402, and a positioningportion is formed in a portion constituting the flange portion 432, forexample, a protruding portion 433 or the like by notching the peripheraledge thereof. In case of forming in this manner, since the closure shell402 is always fixed in a definite direction on the positioning portion,the inner shell 404 can be securely mounted at a determined position.

[0124] In the gas generator formed in the above manner, when the firstigniter 451 arranged in the first combustion chamber 450 provided on theouter side the inner shell 404 is activated, the first gas generatingagent 452 in the combustion chamber 450 is ignited and burnt so as togenerate the combustion gas. And a little gap is obtained between theinner shell 404 and the coolant/filter 425 and this gap allows a gasflow between the coolant/filter 425 and the inner shell 404, andthereby, the combustion gas can effectively use all the surface of thefilter 425. The combustion gas is purified and cooled while passingthrough the coolant/filter 425, and thereafter is discharged from thegas discharge port 410.

[0125] On the other hand, when the second igniter 461 arranged in theinner shell 404 is activated, the second gas generating agent 462 isignited and burnt so as to generate the combustion gas. The combustiongas opens the opening portion 405 of the inner shell 404 and flows intothe first combustion chamber 450 from the opening portion 405.Thereafter, it passes through the coolant/filter 425 as the combustiongas of the first gas generating agent 452 does, and is discharged fromthe gas discharge port 410. The seal tape 429 which closes the gasdischarge port 410 is ruptured by passage of the combustion gasgenerated in the housing 403. The second gas generating agent 462 isignited and burnt due to the activated second igniter 461, and is neverdirectly burnt on the combustion of the first gas generating agent 452.This is because the opening portion 405 of the inner shell 404 is openedonly by the combustion of the second gas generating agent 462 but is notopened by the combustion of the first gas generating agent 452.

[0126] In the gas generator formed in the above manner, the ignitiontimings of two igniters is adjusted such as to activate the secondigniter 461 after activating the first igniter 451, or to simultaneouslyactivate the first igniter 451 and the second igniter 461, and therebyan output's forms (an operating performance) of the gas generator can beoptionally adjusted so that, under various conditions such as a vehiclespeed at a time of collision, an environmental temperature, inflation ofthe air bag can be made most suitable in the air bag apparatus mentionedbelow. Particularly, in the gas generator shown in FIG. 7, twocombustion chambers are arranged in the radial direction, by whereby aheight of the gas generator can be restricted as much as possible.

[0127] Also in the gas generator shown in this drawing, in the samemanner as the gas generator shown in FIG. 1, a plurality of gasdischarge ports 410 formed in the housing 403 are structured such thatthe opening diameter and/or the opening area thereof are controlled intwo or more kinds. Therefore, a difference of the housing maximuminternal pressure at the time when each ignition means is activated issuppressed, the internal pressure at the time when the gas generator isactuated is equalized, which provides a gas generator for an air baghaving a stable combustion performance. Further, also in the gasgenerator according to this embodiment, in the same manner as the gasgenerator shown in FIG. 2, by setting the opening area of each gasdischarge port 410 constant but by changing the thickness of the sealingmeans 429 such as a seal tape so as to adjust the breaking pressure, adifference of the housing maximum internal pressure at the time wheneach ignition means is activated can be suppressed. Further, it isnaturally possible to control both of the opening diameter and/or theopening surface in the gas discharge port 410 and the thickness of thesealing means 429.

[0128] Other Embodiments

[0129] In the gas generator for the air bag shown in Embodiments 1-4mentioned above, it is possible to additionally provide structures whichare optionally made as shown in FIGS. 9-12.

[0130] <Embodiment with Respect to a Through Hole of CombustionChambers>

[0131]FIG. 9 shows another embodiment of an opening portion which isopened by the combustion of the second gas generating agent so as tocommunicate the first combustion chamber with the second combustionchamber.

[0132] That is, FIG. 9a shows an aspect structured such that an openingportion 505 formed on a partition wall 504 (including an inner shell)which defines a first combustion chamber 550 and a second combustionchamber 560 is covered, from an outer side, with a suitably formedshutting plate 590, which is obtained, for example, by forming abelt-like member into an annular shape, and thereby a combustion flameof the first gas generating agent is not directly contacted. Referencenumeral 522 denotes a second gas generating agent. FIG. 9b shows anaspect structured such as to form a notch 512 on a peripheral wall ofthe partition wall 504 so as to form the opening portion 505. Further,FIG. 9c shows an aspect structured such as that a thickness of theperipheral wall of the partition wall 504 is made partly thin so as toform the opening portion 505.

[0133] Accordingly, in the gas generator shown in the above Embodiments1-4, the opening portion which communicates the first combustion chamberwith the second combustion chamber may be formed in the aspect shown inFIG. 9 so as to communicate the first combustion chamber with the secondcombustion chamber.

[0134] <Embodiment with Respect to Structure of Positioning a Igniterand a Cable>

[0135]FIG. 10 shows the positioning structure of two igniters used inthe Embodiment 1-4 and the cable connected so as to transmit theactivating signal to each igniter.

[0136] Namely, the gas generators shown in Embodiments 1-4 include twoigniters, and usually, a cable 515 for transmitting activation signalsis connected to the igniter. In the gas generators shown in Embodiments1-4, this cable 515 transmits, in some cases, different activationsignals to adjust the activating timing of the igniters. In this case,if a wrong cable 515 is connected to the igniter in error, the desiredoutput can not be obtained. Thereupon, the igniter is provided withpositioning means so that each of the igniters can be connected to onlyone of the cables 515, and thereby, connection error can be prevented.Such positioning means can be achieved by using a connector 516 of arespectively different type for each of the igniters as shown inenlarged views of essential portions of FIGS. 10a to 10 d. Inpositioning means shown in FIG. 10a, the connector 516 is formed with apositioning groove (or projection) 517, and a formed position where aprojection (or groove) 518 corresponding to the positioning groove (orprojection) 517 is respectively different for each of the igniters 538.That is, positions of the groove (or projection) 517 of each of theconnectors 516 is changed so that, if the connector 516 is not mountedin the correct direction, the connectors interfere with each other andthey can not be mounted correctly when the connector 516 is mounted tothe gas generator. In positioning means shown in FIG. 10 b, only one ofconnectors 521 is provided with a groove (or projection) 519. Namely, aconnector 521A having the groove (or projection) 519 can be jointed toan igniter 522 b which is not provided with a projection (or groove)520, but a connector 521B which is not provided with the groove (orprojection) 519 can not be jointed to an igniter 522 a having theprojection (or groove) 520. As a result, connection error of theconnector 521 can easily be found at the time of assembling. FIG. 10cshows that shapes of portions 523 to be connected to connectors 539 aredifferent from one another. In FIG. 10d, two connectors are formed intoone, and a positioning groove (or projection) 524 is formed. Other thanthis, as this positioning means, means for eliminating connection errorof the connector can be appropriately employed.

[0137] In this manner, in each of the gas generators of Embodiments 1-4,when the positioning means which identifies the cable 515 to beconnected to each of the igniters is provided, a gas generator for anair bag capable of more reliably adjusting the activation of a gasgenerator is realized.

[0138] And the lead wire connected to each igniter can be, as shown inFIG. 10, taken out in the same direction on the same plane.Particularly, as shown in this drawing, it is preferable to connect eachlead wire via the connector and arrange the connectors on the same planein parallel. The connectors preferably draw out each of the lead wiresin a direction perpendicular to an axial direction of the housing andalso in the same direction.

[0139] <Embodiment with Respect to Coolant/Filter>

[0140]FIG. 11 relates to a structure of a coolant/filter 530 arranged inthe housing and used for purifying and/or cooling the combustion gasgenerated by the combustion of the gas generating means, andparticularly relates to a self-contracting type coolant/filter 530 whichcan prevent a short pass, that is, prevent the combustion gas frompassing between an housing internal surface 531 and the filter 530, inrelation to a shape of the housing internal surface 531.

[0141] That is, the upper and lower end surfaces of the coolant/filter530 are inclined so as to be pressed to the outer side in the radialdirection and disposed in the housing, being in contact with upper andlower inner surfaces of the housing. At this time, it is preferable thatthe upper and lower inner surfaces 531 of the housing are formed so asto be inclined in correspondence to an incline of the upper and lowerend surfaces of the coolant/filter 530. Consequently, the coolant/filter530 which is pushed to the outer side in the radial direction by thecombustion gas are into contact with the inner surface 531 of thehousing, thereby preventing the short pass of the combustion gas betweenthe both members.

[0142] <Embodiment with Respect to an Automatic Igniting Material (AIM)>

[0143]FIG. 12 shows a gas generator for an air bag according to anaspect in which an automatic igniting material (AIM) 385 to be igniteddue to a combustion heat of the first gas generating agent 309 atransmitted from the housing 1 or the like is stored in the secondcombustion chamber. The gas generator shown in this embodiment burnsindirectly the second gas generating agent 309 b stored in the secondcombustion chamber 305 b, due to the combustion of the first gasgenerating agent, which is left unburnt after the actuation of the gasgenerator when only the first gas generating agent 309 a is burnt. Thisembodiment will be described with reference to the gas generator for theair bag shown in the above Embodiment 3.

[0144] Also in the gas generator for the air bag shown in Embodiment 3,the first gas generating agent 309 a and the second gas generating agent309 b are generally ignited and burnt independently by the respectiveactivation of the first igniter 312 a and the second igniter 312 b.Sometimes, only the first igniter is ignited by current and only thefirst gas generating agent 309 a in the first combustion chamber 305 ais ignited and burnt. Namely, the second gas generating agent 309 b andthe second igniter 312 b are left unburnt. Since such a case causes adisadvantage at a time of the later operation, disposal and the like,after the actuation of the gas generator (only the first igniter 312 a),it is preferable to burn the gas generating agent 309 b in the secondcombustion chamber 305 b at a further delayed timing (for example, 100milliseconds or more) than the normal delayed ignition timing (forexample, 10 to 40 milliseconds) for activating the second igniter 312 b.Accordingly, as shown in FIG. 12, the automatic igniting material 385 tobe ignited and burnt due to the conduction of the combustion heat of thefirst gas generating agent 309 a can be arranged in the secondcombustion chamber 305 b. In this case, the ignition of the second gasgenerating agent 309 b by the automatic igniting material 385 isperformed at a further more delayed time than the predetermined delayedtime (that is, an activating interval between the igniters) whennormally activating the second igniter 312 b after the activation of thefirst igniter 312 a. Namely, it is different from the case of delayingthe combustion of the second gas generating agent 309 b (i.e. delayingthe activation of the second igniter 312 b) for the purpose of adjustingthe operating performance of the gas generator. The second gasgenerating agent 309 b is not ignited and burnt by the automaticigniting material 385 during optionally delaying the operating currentto the second igniter 312 b in order to adjust the operating performanceof the gas generator, either. Besides, the automatic igniting material385 can be arranged with being combined with the second igniter.

[0145] This embodiment is particularly described on the basis of the gasgenerator shown in the above Embodiment 3, additionally, in the gasgenerator shown in Embodiments 1, 2 and 4, the automatic ignitingmaterial can be arranged in the second combustion chamber. In this case,even when the second gas generating agent is left unburnt after theactuation of the gas generator, the second gas generating agent can beburnt due to the conduction of the heat generated by the combustion ofthe first gas generating agent.

[0146] Embodiment 5

[0147]FIG. 13 shows an embodiment of an air bag apparatus according tothe present invention in the case of constructing the air bag apparatusin such a manner as to include a gas generator using the electricignition type ignition means.

[0148] The air bag apparatus comprises a gas generator 200, an impactsensor 201, a control unit 202, a module case 203 and an air bag 204. Inthe gas generator 200, the gas generator described with reference toFIG. 1 is used and the actuation performance thereof is adjusted so asto apply as a small impact as possible to the occupant at the initialstage of the actuation of the gas generator.

[0149] The impact sensor 201 can comprises, for example, a semiconductortype acceleration sensor. This semiconductor type acceleration sensor isstructured such that four semiconductor strain gauges are formed on asilicone base plate to be bent when the acceleration is applied, andthese semiconductor strain gauges are bridge-connected. When theacceleration is applied, the beam defects and a strain is produced onthe surface. Due to the strain, a resistance of the semiconductor straingauge is changed, and the structure is made such that the resistancechange can be detected as a voltage signal in proportion to theacceleration.

[0150] The control unit 202 is provided with an ignition decisioncircuit, and the structure is made such that the signals from thesemiconductor type acceleration sensor is inputted to the ignitiondecision circuit. The control unit 202 starts calculation at a time whenthe impact signal from the sensor 201 exceeds a certain value, and whenthe calculated result exceeds a certain value, it outputs an activatingsignal to the igniter 12 of the gas generator 200.

[0151] The module case 203 is formed, for example, by a polyurethane,and includes a module cover 205. The air bag 204 and the gas generator200 are stored in the module case 203 so as to be constituted as a padmodule. This pad module is generally mounted to a steering wheel 207when being mounted to a driver side of an automobile.

[0152] The air bag 204 is formed by a nylon (for example, a nylon 66), apolyester or the like, is structured such that a bag port 206 thereofsurrounds the gas discharge port of the gas generator and is fixed to aflange portion of the gas generator in a folded state.

[0153] When the semiconductor type acceleration sensor 201 detects theimpact at a time of collision of the automobile, the signal istransmitted to the control unit 202, and the control unit 202 startscalculation at a time when the impact signal from the sensor exceeds acertain value. When the calculated result exceeds a certain value, itoutputs the activating signal to the igniter 12 of the gas generator200. Accordingly, the igniter 12 is activated so as to ignite the gasgenerating agent, and the gas generating agent burns and generates thegas. The gas is discharged into the air bag 204, by whereby the air bagbreaks the module cover 205 so as to inflate, thereby forming a cushionabsorbing an impact between the steering wheel 207 and the occupant.

[0154] Embodiment 6

[0155]FIG. 14 is a vertical cross sectional view which shows a secondembodiment of a gas generator for an air bag according to the presentinvention. The gas generator shown in this drawing is also structured tobe particularly suitable for being arranged in a driver side. However, aflow passage forming member 51 is arranged in the first combustionchamber 5 a, and a flow passage 52 through which the combustion gasgenerated in the second combustion chamber 5 b passes is formed betweenthe flow passage forming member 51 and the ceiling portion inner surface28 of the diffuser shell.

[0156] The flow passage forming member 51 is formed into an annularshape obtained by bending an inner periphery and an outer periphery of acircular member so as to form an inner peripheral wall 53 and an outerperipheral wall 54, and a supporting wall 56 for forming a space withthe ceiling portion inner surface 28 of the diffuser shell is integrallyformed on a circular portion 55 connecting the both peripheral wallsurfaces. Then, the flow passage forming member 51 holds the innercylindrical member 4 with the inner peripheral wall 53 thereof andbrings a supporting wall 56 in contact with the ceiling portion innersurface 28 of the diffuser shell, by whereby a fixed space is obtainedbetween the circular portion 55 and the ceiling portion inner surface 28of the diffuser shell. And since multiple through holes 57 are formed onthe supporting wall, the space can function as a gas flow passage 52.The gas flow passage 52 is communicated with the second combustionchamber 5 b by the through hole 10 of the inner cylindrical member 4 dueto the combustion of the gas generating agent 9 b in the secondcombustion chamber 5 b. Therefore, the combustion gas generated in thesecond combustion chamber 5 b is discharged to the gas flow passage 52from the through hole 10, passes through the coolant/filter 22 and isdischarged from the gas discharge port 26.

1. A gas generator for an air bag, comprising a housing forming an outershell container and accommodating two or more ignition means to igniteon an impact and two or more gas generating means which are to beindependently ignited and burnt by the ignition means so as to generatea combustion gas for inflating an air bag, and a plurality of gasdischarge ports which are formed in the housing and closed by sealingmeans for maintaining an internal pressure of the housing to the givenpressure, wherein a breaking pressure for breaking the sealing means isadjusted at multiple stages by two or more gas discharge ports and/ortwo or more sealing means.
 2. A gas generator for an air bag accordingto claim 1, a difference in maximum internal pressures in the housing atthe time of activation of the respective ignition means is suppressed.3. A gas generator for an air bag according to claim 1 or 2, wherein aratio of different breaking pressures with respect to the gas dischargeports being next to each other in pressure for breaking the sealingmeans is 1.1/1 or greater.
 4. A gas generator for an air bag accordingto any one of claims 1 to 3, wherein the breaking pressure is adjustedby arranging two or more kinds of opening diameters and/or opening areasof the gas discharge ports.
 5. A gas generator for an air bag accordingto claim 4, wherein the opening diameter is 1 to 8 mm.
 6. A gasgenerator for an air bag according to claim 4 or 5, wherein among twokinds or more of gas discharge ports formed in the housing, with respectto two kinds being next to each other in size of the opening diameter, aratio between the larger diameter-having gas discharge port and a smalldiameter-having is 4/1 to 1.1/1 and/or a ratio in opening area is 97/3to 3/97.
 7. A gas generator for an air bag according to any one ofclaims 1 to 3, wherein the breaking pressure is adjusted by arrangingtwo or more kinds of thicknesses of the sealing means.
 8. A gasgenerator for an air bag according to claim 7, wherein the openingdiameter is 1.1 to 8 mm.
 9. A gas generator for an air bag according toclaim 7 or 8, wherein among the sealing means having two or more kindsof thicknesses, with respect to two kinds of sealing means being next toeach other in thickness, a thickness ratio between them is 1.1/1 to12/1.
 10. A gas generator for an air bag according to any one of claims7 to 9, wherein adjustment of the breaking pressure is performed bysetting an area ratio of the two kinds or more of gas discharge portshaving different areas that are sealed by the sealing means having twoor more different thicknesses is 97/3 to 3/97.
 11. A gas generator foran air bag according to any one of claims 1 to 3, wherein the breakingpressure is adjusted by arranging two or more kinds of opening diametersand/or opening areas of the gas discharge ports, and by arranging two ormore kinds of thicknesses of the sealing means.
 12. A gas generator foran air bag according to claim 11, wherein the opening diameter is 1 to 8mm.
 13. A gas generator for an air bag according to claim 11 or 12,wherein adjustment of the breaking pressure is performed by setting anarea ratio of the two kinds or more of discharge ports which are sealedby the sealing means having two or more different thicknesses is 97/3 to3/97.
 14. A gas generator for an air bag according to any one of claims1 to 13, wherein the sealing means comprises a seal layer having athickness of 20 μm to 200 μm, an bonding layer or a adhesive layerhaving a thickness of 5 to 100 μm.
 15. A gas generator for an air bagaccording to any one of claims 1 to 14, wherein each of the gasgenerating means for generating the combustion gas is accommodated inindividual combustion chamber and independently ignited by therespective ignition means, and a flame by combustion of one gasgenerating means is not transferred to the other gas generated means.16. A gas generator for an air bag according to claim 14, wherein thegas generating means accommodated in the respective combustion chamberhas a different surface area per unit weight from each other.
 17. A gasgenerator for an air bag according to claim 1, wherein in the housing,two combustion chambers storing the gas generating means areconcentrically provided so as to be adjacent in the radial direction ofthe housing, and a communicating hole which allows communication betweenthe combustion chambers is provided.
 18. A gas generator for an air bagaccording to claim 1, wherein the housing is formed into a cylindricalshape having an axial core length longer than an outermost diameter, thehousing is provided at its peripheral wall with a plurality of gasdischarge ports, two combustion chambers storing the gas generatingmeans are concentrically provided so as to be adjacent in the axialdirection and/or a radial direction of the housing, and a communicationhole which allows communication between the combustion chambers isprovided.
 19. A gas generator for an air bag according to claim 1,wherein the respective igniters constituting the ignition means areprovided in one initiator collar so as to be aligned to each other inthe axial direction.
 20. A gas generator for an air bag according toclaim 19, wherein the ignition means comprises a transfer charge to beignited and burnt on activation of the igniter, the transfer charge ispartitioned for each igniter and independently ignited and burnt at eachigniter, and the gas generating means accommodated in the two combustionchambers are ignited and burnt by flame respectively caused bycombustion of the transfer charge in different section.
 21. A gasgenerator for an air bag according to any one of claims 1 to 20, whereinthe two or more ignition means include igniters which are to berespectively activated on electric signals, the igniters are provided inone initiator collar so as to be aligned to each other in the axialdirection, and each igniter is arranged eccentrically with respect tothe center axis of the housing.
 22. A gas generator for an air bagaccording to any one of claims 1 to 21, wherein the two or more ignitionmeans include igniters which are to be respectively activated onelectric signals, lead wires for transmitting the electric signals arerespectively connected to the igniters, and the lead wires are taken outin the same direction on the same plane.
 23. A gas generator for an airbag according to any one of claims 1 to 22, wherein the two or moreignition means include igniters which are to be respectively activatedon electric signals, lead wires for transmitting the electric signalsare respectively connected to the igniters via connectors, and theconnectors are arranged in the same direction on the same plane.
 24. Agas generator for an air bag according to any one of claims 1 to 23,wherein the two or more ignition means include igniters which are to berespectively activated by electric signals, lead wires for transmittingthe electric signals are respectively connected to the igniters viaconnectors, and the lead wires are taken out in the same directionperpendicular to the axial direction of the housing by the connector.25. A gas generator for an air bag according to any one of claims 1 to24, wherein the two or more ignition means include igniters which are tobe respectively activated by electric signals, lead wires fortransmitting the electric signal are respectively connected to theigniter by connectors, and the connectors have positioning means capableof connecting to only one of the igniters.
 26. A gas generator for anair bag according to claim 25, wherein the positioning means is formedinto a connector shape which is different at each connected igniter. 27.A gas generator for an air bag according to claim 25 or 26, wherein thepositioning means is a groove and/or a projection which is formed in theconnector so as to be different in a position and/or a shape at eachconnected igniter.
 28. An air bag apparatus comprising: a gas generatorfor an air bag; an impact sensor for detecting an impact and activatingthe gas generator; an air bag to introduce a gas generated in the gasgenerator and inflate; and a module case for storing the air bag,wherein the gas generator for the air bag is the gas generator for theair bag according to any one of claims 1 to
 27. 29. A method ofcontrolling gas generation, comprising adjusting a breaking pressure forbreaking the sealing means at multiple stages by two or more gasdischarge ports and/or two or more sealing means in a gas generator foran air bag comprising a housing forming an outer shell container andaccommodating two or more ignition means to ignite on an impact and twoor more gas generating means which are to be respectively ignited andburnt by the ignition means so as to generate a combustion gas forinflating an air bag, and a plurality of gas discharge ports which areformed in the housing and closed by sealing means for maintaining aninternal pressure of the housing to the given pressure.
 30. A gasgenerator for an air bag, comprising a housing forming an outer shellcontainer and accommodating two or more ignition means to ignite on animpact and two or more gas generating means which are to be respectivelyignited and burnt by the ignition means so as to generate a combustiongas for inflating an air bag, and a plurality of gas discharge portswhich are formed in the housing and closed by sealing means formaintaining an internal pressure of the housing to the given pressure,wherein a first combustion chamber which starts burning first and asecond combustion chamber which starts burning later are partitioned bya wall having a communication hole, the communication hole is providedwith flame-transfer-preventing means so that the combustion in thesecond combustion chamber should not be caused by the combustion in thefirst combustion chamber.
 31. A gas generator for an air bag accordingto claim 30, wherein the flame-transfer-preventing means is a sealingmember.
 32. A gas generator for an air bag according to claim 31,wherein the sealing member seals the communication hole on the side ofthe first combustion chamber.
 33. A gas generator for an air bagaccording to claim 31 or 32, wherein the flame-transfer-preventing meansis a seal tape which seals the communication hole on the side of thefirst combustion chamber.
 34. A gas generator for an air bag accordingto claim 31 or 32, wherein the flame-transfer-preventing means is asealing plate.
 35. A gas generator for an air bag, comprising a housingforming an outer shell container and accommodating two or more ignitionmeans to ignite on an impact and two or more gas generating means whichare to be respectively ignited and burnt by the ignition means so as togenerate a combustion gas for inflating an air bag, and a plurality ofgas discharge ports which are formed in the housing and closed bysealing means for maintaining an internal pressure of the housing to thegiven pressure, wherein the first combustion chamber which startsburning first is partitioned from the second combustion chamber whichstarts burning later, and the gases generated in the respectivecombustion chambers pass through different passages and reach the gasdischarge ports.
 36. A gas generator for an air bag according to claim35, wherein different passages are formed by passage forming members.